Seven-Step Formal Synthesis of 9-epi-Parvistemonine A

Herein, we report a concise formal synthesis of an epimer of the alkaloid parvistemonine A, starting from the inexpensive and readily available D-glucono-δ-lactone as the sole chiral pool source. The synthesis features a one-pot lactone formation and the direct functionalization of commercially available pyrrole, enabling the convergence of two simple building blocks through a cross-metathesis reaction. This key transformation is followed by a stereoselective intramolecular Michael-type cyclization under acidic conditions, forging a seven-membered ring and establishing the desired framework. Notably, the synthesis proceeds without the use of protecting groups and delivers the tricyclic Stemona backbone in only seven steps, with the cis-fused 5/7/5 framework confirmed by single-crystal X-ray crystallography.